Hydrazine salts synthesis

Although it has long been known that benzaldehyde reacts with hydrazine in alkaline solution to give a yellow, insoluble precipitate of benzalazine1 and that the latter when steam distilled in the presence of mineral acids is hydrolyzed to give the corresponding hydrazine salts,2 no previous attempt has been made to apply these facts to the recovery of hydrazine residues. This reaction is practically quantitative and can be applied not only to the recovery of residual hydrazine left in solution in the Raschig synthesis (No. 31) but to all solutions where the detection and recovery of hydrazine in the presence of ammonia, or hydroxylamine, are of interest. In the process of formation of hydrazine salts from benzalazine, 95 per cent of the benzaldehyde can be recovered. 

The schematic of the process is shown in Fig. 28.29. The manufacturing procedure is divided into five major steps the synthesis of azine, the removal of low boilers, high boilers separation, hydrolysis of azine, and the dehydration of hydrazine. The synthesis of azine requires a residence time of 7 hours. Ammonia, hydrogen peroxide, and methyl ethyl ketone (MEK) are fed into the reactors along with methanol and acetonitrile at about 50°C. Small amounts of the disodium salt of ethylenediamine tetracetic acid are added to the reactants. In the low-boilers removal step, the unreacted ammonia, MeOH, MEK, and acetonitrile are separated and recycled to the reactors. The high-boilers solution contains water, MEK-azine, and acetamide. The acetamide is formed in the following reaction ... 

Common synthetic methods practiced for the preparation of metal hydrazines, and some single-crystal structures, are discussed briefly in Chapter 1. A direct method of synthesis of metal hydrazines has been developed that involves adding metal powders to hydrazine salts (preparation of salts discussed in Chapter 2). Details of the synthesis of several simple and mixed metal hydrazines by this and other methods, along with their spectral characterization and thermal reactivity, are now described. 

Hydrazine as Nucleophile. Reaction of hydrazine and carbon dioxide or carbon disulfide gives, respectively, hydrazinecarboxyhc acid [471-31-8], NH2NHCOOH, and hydrazinecarbodithioic acid [471-32-9], NH2NHCSSH, in the form of the hydrazinium salts. These compounds are useful starting materials for further synthesis. For example, if carbon disulfide reacts with hydrazine in basic medium with an alkyl haUde, an alkyl dithiocarbazate ester is obtained in a one-step reaction ... 

Aromatic Hydrazines. A general synthesis for aryUiydraziaes is via diazotization of aromatic amines, followed by reduction of the resulting diazonium salt (18) ... 

The most important synthesis of pyrazolones involves the condensation of a hydrazine with a P-ketoester such as ethyl acetoacetate. Commercially important pyrazolones carry an aryl substituent at the 1-position, mainly because the hydrazine precursors are prepared from readily available and comparatively inexpensive diazonium salts by reduction. In the first step of the synthesis the hydrazine is condensed with the P-ketoester to give a hydrazone heating with sodium carbonate then effects cyclization to the pyrazolone. In practice the condensation and cyclization reactions are usually done in one pot without isolating the hydrazone intermediate. 

Sanofi-Synthelabo researchers discovered pyrazole 53 and analogs to have potent Cannabinoid receptor-1 (CB-1) antagonist/inverse agonist activity and have progressed 53 into development for treatment of obesity and alcohol dependence. The synthesis of 53 was accomplished by heating the diketone sodium salt 51 with the aryl hydrazine hydrochloride in acetic acid to provide the intermediate 52, which was further derivatized... 

Azelastine (107) is an antiallergic/antiasthmatic agent prepared from 4-chlorobenzyl-2 -car-boxyphenylketCHie (105) by condensation with hydrazine to give the phthalazinone (106) followed by reaction of the sodium salt of this last with 2-(2-chloroethyl)-N-methylpyrrolidine (presumably involving nucleophilic ring expansion of the bicyclic quaternary salt putatively formed as a first product) to complete the synthesis [30]. 

The formation of semiconductor nanoparticles and related stmctures exhibiting quantum confinement within LB films has been pmsued vigorously. In 1986, the use of the metal ions in LB films as reactants for the synthesis of nanoscale phases of materials was described [167]. Silver particles, 1-2 mn in size, were produced by the treatment of silver be-henate LB films with hydrazine vapor. The reaction of LB films of metal salts (Cd, Ag, Cu, Zn, Ni, and Pb ) of behenic acid with H2S was mentioned. The use of HCl, HBr, or HI was noted as a route to metal halide particles. In 1988, nanoparticles of CdS in the Q-state size range (below 5 mn) were prepared inside LB films of cadmium arachi-... 

Until recently it was thought that mono-substituted hydrazines invariably reacted with 5-methylisothiouronium salts to give compounds of type (XVII) [129, 192, 193] however, examples have now come to light in which the alternative isomer (XVI) has been isolated from this reaction [21, 131, 194, 195). This formulation is based on (a) the failure of the products to react with benzaldehyde, [21, 129, 131, 194], (b) the unambiguous synthesis of the two possible alternative structures [21, 129, 194], and (c) an examination of the nuclear magnetic resonance spectra of the mono- and di-protonated forms of some... 

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